A study presented earlier this month at a meeting of the
American Urological Association by a team of French researchers found that a
particular dog breed, Belgian Malinois shepherd dogs, can be trained to detect
prostate cancer.

Doctors at Paris's Hospital Tenon trained the dogs to
distinguish between the smell of urine from men with prostate
cancer and those without it. At the end of the training and study the dogs
correctly identified 63 out of 66 samples.

It sounds bizarre, but there might be something to it. Many animals have
far keener senses than humans; cats can see in near darkness, elephants'
sensitive feet can detect the footsteps of other elephants miles away, and so
on. Dogs are of course known for their remarkable sense of smell,
which is why they are used by law enforcement to sniff out drugs, explosives
and escaped prisoners.

Canine sense of smell is said to be 100,000 times more acute
than ours, and prostate cancer cells may release distinct odors. Lead
researcher Jean-Nicolas Cornu concluded that the dogs "are certainly
recognizing the odor of a molecule that is produced by cancer cells."
While the new research is promising, the real value would be in identifying the
specific molecules the dogs are detecting.

Some scientists are cautiously optimistic, noting that the
study is a small one, and must be replicated by other researchers to prove there
is a real effect. There is also the potential study design problem that the
dogs might have been able to pick up subconscious cues from the researchers
about which samples were cancerous and which were not. In research this
influence is called the "Clever Hans effect," after a horse named
Hans that, in early 1900s Germany, was claimed to be able to solve math
problems, read and understand German, and other amazing abilities. Careful
skeptical investigation revealed that Hans merely gave the illusion of being
able to do these tasks; he was instead reacting to subtle (and unconscious)
cues from his trainer.

If the study can be replicated, the dog-sniffing prostate cancer screening
would be more accurate than the blood test currently used, which detects elevated
levels of a prostate-specific antigen (PSA) protein and has a high rate of
false positives.

Benjamin Radford is managing editor of the Skeptical Inquirer science magazine. His new book is Scientific Paranormal
Investigation; this and his other books and projects can be found on his website. His Bad Science column
appears regularly on LiveScience.